hes grown up indeed. I thought he would pussy out and hide the fact he has a girlfriend to her until the very moment it gets accidentally revealed. Hagiwara was probably going to say for him to wait before she gives a response.
Since Hamaji is this sincere, next for Hayami's sake she should be more aggressive to keep the relationship afloat or else she'll just give him away due to her insecurities again. or I should say both of them should start getting serious in the relationship. to start He should reassure hayami he told Hagiwara off
knowing mangas like these tho I dont feel the relationship is gonna last long